I always precondition my Volt prior to leaving home in summer and winter while plugged into a Level 2 EVSE. When away from home I will also precondition when not plugged in, again to cool down a hot interior or warm up the cabin before I re-enter the vehicle. Yes, it uses some power from the battery to do so but if the vehicle was recently warmed up prior to again preconditioning the hit on the EV range is not that great. Also, if it is cold enough then the ICE will start when preconditioning due to the cold temperature and that warms the car without using much of the battery.
The precondition cycle lasts 10 minutes although you can extend it for an additional 10 minutes. If the ICE starts due to the outside temperature being lower than 35F/2C, or 15F/-9C if Engine Assist Heat is set to Deferred, then the ICE will only run until the engine coolant temperature reaches 147F/64C then cycles off. The ICE may not need to run for the full 10 minutes, so maybe only the first 5 minutes of the entire preconditioning cycle.